The invention relates to electrical circuit arrangements and more particularly to electrical circuit arrangements for synchronising electrical signals such as trains of data pulses.
A requirement often exists for synchronising two pulse trains. For example, it may be desirable to produce in a receiver a train of pulses which are synchronised with the bit rate of data received over a transmission link. Even though normally the bit rate will be nominally constant, it is necessary to make adjustments from time to time in the phase of a pulse train generated in the receiver--to take account of inevitable drift and other similar factors. It is known to transmit a synchronising signal over such a transmission link for carrying out this phase adjustment but this is wasteful of transmission capacity.
Furthermore, a system which periodically measures the phase difference between a pulse train at a receiver and the bit rate of the received signal and simply produces a correction dependent on this phase difference may not be completely satisfactory, because the phase difference measured at that instant may not be representative of the phase difference at other times.